Many websites feature advertisements for products and services that are positioned alongside other content of a web page. In some cases, the ads can be related to the subject matter of the web page. For example, a web page about a tourist destination may include ads for shops, restaurants and other attractions at or near that destination. In these cases, the advertising is determined primarily by the content of the website and all visitors to the website will see the same ads. In some other cases, tracking software, such as cookies, can be used to generate a profile of a particular user as that user browses various websites. The profile may, for example, describe which web pages the user visited, as well as when and how often those pages were visited. This profile can in turn be used to target that particular website visitor with ads that are relevant to the perceived interests of the visitor, based on the content of the web pages that visitor previously viewed. However, these techniques only take into account the content of the entire web page. Furthermore, any targeted advertising only appears during subsequent visits or page loads, which may occur over a period of hours, days or even months. Thus, the ads may not be of immediate interest to a visitor who is actively seeking specific information about a certain subject, and consequently such targeted ads are often ignored.